2-(2-thiazylthio)-1,4 dihydroxybenzenes and process for the preparation of same



Patented Nov. 4, 1952 2,616,893 H v 2;:(2 qrmrlz'ytrmm 1,4DIHYDR'OXYBEN-. ZENES AND PROCESS FOR THE PBEPARAM,

TIONOF SAME Tho'ni'asfi. NewbygWaterbijiry, cams, ssigns? to I Unitedstates Rubber company, New York; N, ,Y. zit-corporation of New Jersey NeDra 'n' g; Ori'giii@tl applicants April 7, 1949,

- erial No. 86.108. Divided and this application March is," 1991; SerialNo. 215,860

,This invention-relates icals and to use thereof as antioxidants fororganic substances such as natural rubber and synthetic rubber,particularly rubbery copolymers' of butadiene and styrene and rubberycopolymers of butadiene and acrylon itrile, which are sus-'- ceptible todeterioration by atmospheric oxygen.

The principal object of the present invention is to make available a newclass of chemical compounds which are particularly valuable asantioxidants. Another object is-to protect organic materials,particularly natura1 and synthetic rubber, against the deteriorationwhich normally occurs when these materials" are exposedtd the action ofatmospheric oxygen. Another object is to provide a non-staining"and'nohdiscoloring antioxidant. Numerous other objects;v will morefullyhereinafter ap ear:

The chemicaf c mpounds of t le presentmvention' are" the2-(2thiazylthid)'-l,4-dihydroXyberizenes'having the general formulaR-C-N where R and R may be hydrogen, alkyl, aryl; or part of av ring"-system. The groupsR and R, orv the ring of which they are a part may besubstituted' with groups which do not interfere with theantijoxidantaction of the compound and which do not interfere thefoririatic'n 6f the compound in accordance with Equations 1 and 2 below,examples of su'ch substi'tuent groups being nitro and hydroxy as well asalkylsucl' i a's methyl and ethyl.

to a new class of chem- The eomwmrs or my iii eiitio'r'i'convniently 1may be designated as 2"-ca thiaz nhidi-hydiouindriesofth benzr'ie'series. v l The chemical eomndurids of; my invention may be readily preparedby reacting; a Z-friercaptothiaz'ole with p"-beh'zliq1iirione as,showripbythe following equation":

The reaction is typically carries out byreactina equal: molar quantitiesof fl-benz oquinone, and-- the 2-mercaptothiazole an inert solvent attemperatures-varying from 1i)C.-toth'eboi1ingpbint'ofthesolve'nt. Aftertlfe reactionhas'at trained the desired degree of completion;the'prodmaking the: compounds of ifiVliti'dfl, Iifiay use1,4benzoquinones substituted in suitable positions with suitable groupswhich do not intrf'ere withth' a tidxidant action of tliecoinpound" andwhich do not interfere the for mason of the cdrri'fioufid' themamrr'described above, foifsaiuple with alkyl, alkoxy, riitr'oj, and riyur-uxygroups. At feast one positron ortho to one or carbonyl grc'cps si cuidteu'r'isubsti' fluted and any substitutio ri' i'ri other positions shouldbe as to all the reaction outlined above to take place an "of-t6"interfere with the antioxidafifi action. Possiblesubs'tituted"duinoiiesfor" use in" this racti'oiiwili be straight-w those skilled in the art.The most preferred compounds of my invention are those fii'ald''fi'b'l'fi p-bnz'oquinone.

Exam les" 6f ql'iil'idfils' (ith'f' than p-bemo quinone which can beused include:

2,5-ditertiarybutyl p benzoquinone methoxy-pbenzoquinone2,5-dimethyl-p-benzoquinone 3-, 5 dimethyl-p-benzoquinonenitro-p-benzoquinone hydroxy-p-benzoquinone The following-' examplesillustrate the preparatiye mstiied more fully.

' Example L B-(AZ-beneathiazylthio) 1,4 dz- Iiydrogcyhe1'iee1ie. Quinone(22 g.) was dissolved in 150101-01 boiling methanol and the solutionco'oled' rapidly td 05 C. in an ice bath whereupon the quinonecrystallized in fine needles.

To this mixturea' slurry of 33 g. of Z-mercaptobenzothiazoleill-10006101 ice-cold methanol was added. Theirfea'ctionfmixture wasthen stirred for two hours at 0-5" C.

The product was isolated by filtering oil the small amount ofmethanol-insoluble material and. then quenching the methanol solution in500 cc. of hot water. The mixture was boiled and the lumps broken upuntil no longer sticky. After filtration and drying 42 g. (76% yield) ofcrude 2-(2-benzothiazylthio) 1,4 dihydroxybenzene melting 204.5 208 C.was obtained. After recrystallization from ethyl acetoacetate it melted2l8219 C.

The material melting '239-247 C. was shown by analysis to be a mixtureof monoand disubstituted 1,4-dihydroxybenzene.

Any of the compounds of my invention may be employed as antioxidants forthe organic sub stance to be protected against oxidative deteriora--tion. In practice, a suitable amount of the chemical is incorporateduniformly into the material to be protected, usually by simple physicaladmixture in any suitable equipment. The amount Hydroused should be suchas to give the desired degree Analysls Garb gen gen of protection.Usually an amount ranging from 0.05 to 5.0 parts per 100 parts oforganic sub- Found 56.0 28-42 stance will be used. In the case ofrubber, an 23'27 5 amount Of the order of 0.05 to 5.0 parts per 100parts of rubber will be sufiicient to give excellent Example II .-2- [2-4,5-dimethyl thzazylthzo) resistance t ti 1,4-dihydroxybenzene.Quinone(11 g.) was p The compounds of the present invention are Cipitated inmethanol as in a ple and effective antioxidants for natural rubber orany f y C D in 100 0f synthetic rubber which is normally subject todeice-cold methanol were added to the slurry. The t i ti upon contactwith oxygen. Examples reaction mixture was stirred for two hours at ofsuch synthetic rubbers include the rubbery 0-5 C. copolymers ofbutadiene and styrene and the The product was worked up by removing mostrubbery copolymers of butadiene and acryloniof the methanol undervacuum, and then pourtri1e ing the residue into 300 cc. of hot water.After Rubber antioxidant tests gfi n :g gig g gi i gif fg ggi Thefollowing tests illustrate the use of com- 9 pr y pounds of the presentinvention as rubber antithiazylthio) 1,4 d1hydroxybenzene were ob- 0X1dams, tained. Treatment of this material with hot methanol gave 20 g. ofa methanol-soluble solid gifii fig s i Exammes II and 2- o L y o) 1,4dihydroxybenzene, 2- meltlng 148-152 C. and a small amount or [2 (4 5dimeth yl th1azy1th1o)l 1,4 dihydroxymethanol-msoluble mater1a1. Theyield of the benzene nd 1 thiaz )1 14 ethanol-soluble product was 79%. ay y m dihydroxybenzene were tested in a white natural rubber stock ofthe following composition: Analysis Nitrogen Sulfur Parts by weightFound 5. 37 25. 59 Pale crepe 100 Theory for CllHllOzNSz 5- 54 25-30Zinc oxide 10 4O Lithopone 60 x hiting 60 Example III.-2-[2-(4-methylthzazylthzo) 1,4-dihydmxybenzena-Quinone (21 g.) and 4- Zmc laura'temethyl-2-mercaptothiazole (26 g.) were reacted sulphur as described inExample II for the dimethyl body. Tetmmethyl thluram monosulfide Theproduct was worked up by filtering off the The use of theherein-disclosed chemicals for methanol-insoluble material (11 g.melting 239- the protection of rubber against deterioration 247 C.) andthen quenching the methanol filtrate upon contact with oxygen is thesubject matter with hot water. After boiling the water soluof copendingapplication Serial No. 86,108, filed tion for a short time the solidswere filtered off. April 7, 1949, of which the instant application Theproduct when dry weighed 32 g. (67% yield) is a division. and melted158-161 C. after two washings with The antioxidant was incorporated inthe ratio 1 benzene of 1.0 part per 100 parts of rubber. Cures were madefor 10, 20 and 30 minutes at 30 pounds Analysls Nitrogen sulfur steampressure. Table I shows the tensiles and elongations of these stocksunaged, after aging Found 5 g9 2104 o ninety-six hours under 300 poundsOf oxygen Theoryfor O10HQO1N 2 26-89 pressure at C. and after aging forfortyeight hours at C. in an air oven.

Unaged Heat Aged Oxygen Aged Antioxidant 9 'r E 'r E 'r E None 10 2, 340663 660 500 990 510 A. (2-(2-benzothiazylthio -l,4-dihydroxybenzene)2,330 650 890 503 1,870 505 B. (2-[2-(4,6-d 1 m e t h ylth1azylth1o)]-1,4-

dihydroxybenzene) 2.415 660 1,036 540 2, 040 610 C. (2-[2-(4-methylthiazylthio)]-l,4-dihydroxybenzene) 2, 350 655 930 476 1,950 620 None 202,080 045 700 400 failed 11.- 2,020 005 840 400 1.660 540 B 2. 004 645750 405 1,720 510 0.- 2, 030 636 880 455 1,810 000 None 30 2,080 050 000500 failed A 2.130 645 680 42s 1, 480 545 B 2,075 055 870 470 1, e00 575o 2,010 640 040 40s 1, 700 010 Ttensile.

I l-elongation.

The crude methanol-insoluble materials obtained in the three examplescited (mixtures of the monoand di-substituted 1,4-dihydroxybenzenes) andthe quinones obtained by oxidation of the primary products are alsoexcellent antioxidants for rubber.

The chemicals of this invention are of value as antioxidants forsynthetic rubber. For example, 2 (2 benzothiazylthio) 1,4dihydroxybenzene, when incorporated into butadiene-styrene copolymer(GR-S) in the ratio of 1.5 parts per 100 parts of polymer, protected thepolymer against resinification for eleven hours at 130 C. The controlresinified in one and one-half hours.

While the invention has been particularly described for2-(2-thiazylthio) -1,4-dihydroxybenzenes, it is equally applicable toother quinonemercaptothiazole compounds such as:

2 (2 benzothiazylthio) 1,4 dihydroxy 5- methylbenzene 3 (2benzothiazylthio) 1,4 dihydroxy 2,5-

ditertiary-butylbenzene Y 2 [2 (4 methyl thiazylthio)] 1,4dihydroxy-fi-methoxybenzene 2 (6 nitrobenzothiazyl 2 thio)1,4-dihydroxybenzene 2 (6 aminobenzothiazyl 2 thio) 1,4-dihydroxybenzene2 (6 hydroxybenzothiazyl 2 thio) 1,4-

dihydroxybenzene 2- [2 (4 phenylthiazylthiOH -'1,4 dihydroxybenzene 2 [2(4,5 diethyl thiazylthio)] 1,4-dihydroxybenzene The antioxidants of myinvention have the great advantage that in addition to their excellentantioxidant properties they do not discolor organic materials uponexposure to light nor do they stain lacquers or cloth with which theycome in contact. This is particularly important in the case of use withrubber to make lightcolored or white stocks or articles.

Having thus described my invention what I claim and desire to protect byLetters Patent is:

1. As a new chemical compound, a 2-(2- thiazylthio)-1,4-dihydroxybenzene.

2. As anew chemical compound, 2-(2-benzothiazylthio)-1,4-dihydroxybenzene.

3. As a new chemical compound, 2-[2-(4,5- dimethyl thiazylthio)]-1,4-dihydroxybenzene.

4. As a new chemical compound, 2-[2-(4- methyl thiazylthio)]-1,4-dihydroxybenzene.

5. The method which comprises bringing together a 1,4-dihydroxybenzeneand a 2-mercaptothiazole in approximately equimolar proportions in aninert solvent for the reactants at a temperature ranging from 10 C. tothe boiling point of said solvent, and after the reaction has attainedthe desired degree of completion recovering from the reaction mixture a2-(2- thiazylthio) -1,4-dihydroxybenzene.

6. The method of claim 5 wherein said 1,4- dihydroxybenzene isp-benzoquinone and wherein said z-mercaptothiazole isz-mercaptobenzothiazole.

7. The method of claim 5 wherein said 1,4- dihydroxybenzene isp-benzoquinone and wherein said Z-mercaptothiazole is4,5-dimethyl-2-mercaptothiazole.

8. The method of claim 5 wherein said 1,4-dihydroxybenzene isp-benzoquinone and wherein said 2-mercaptothiazole is4-methyl-2-mercaptothiazole.

9. The method of claim 5 wherein said inert solvent is methanol andwherein the reaction is carried out at a temperature of from 0 to 5 C.

THOMAS H. NEWBY.

N 0 references cited.

1. AS A NEW CHEMICAL COMPOUND, A 2-(2THIAZYLTHIO)-1,4-DIHYDROXYBENZENE.